Get your stuff oil-wise from a moto shop. Way cheaper, and you'll have plenty for many, many oil changes down the road.

When swapping the spring, you don't need to remove the lowers at all. Have the fork sitting flat (so no oil leaks out top or bottom) pull old spring out, pop new in, do up the lower bolt and topcap. Good to go with minimal oil loss. As you've noted, the coil side only uses a tiny amount.